Temperature and salinity variations of Mediterranean Sea surface waters over the last 16,000 years from records of planktonic stable oxygen isotopes and alkenone unsaturation ratios

Temperature and salinity variations of Mediterranean Sea surface waters over the last 16,000... Alkenone unsaturation ratios and planktonic δ 18 O records from sediment cores of the Alboran, Ionian and Levantine basins in the Mediterranean Sea show pronounced variations in paleo-temperatures and -salinities of surface waters over the last 16,000 years. Average sea surface temperatures (SSTs) are low during the last glacial (averages prior to 13,000 years: 11–15°C), vary rapidly at the beginning of the Holocene, and increase to 17–18°C at all sites during S1 formation (dated between 9500 and 6600 calendar years). The modern temperature gradient (2–3°C) between the Mediterranean sub-basins is maintained during formation of sapropel S1 in the Eastern Mediterranean Sea. After S1, SSTs have remained uniform in the Alboran Sea at 18°C and have fluctuated around 20°C in the Ionian and Levantine Basin sites. The δ 18 O of planktonic foraminifer calcite decreases by 2‰ from the late glacial to S1 sediments in the Ionian Basin and by 2.8‰ in the Levantine Basin. In the Alboran Sea, the decrease is 1.7‰. Of the 2.8‰ decrease in the Levantine Basin, the effect of global ice volume accounts for a maximum of 1.05‰ and the temperature increase explains only a maximum of 1.3‰. The remainder is attributed to salinity changes. We use the temperature and salinity estimates to calculate seawater density changes. They indicate that a reversal of water mass circulation is not a likely explanation for increased carbon burial during S1 time. Instead, it appears that intermediate and deep water formation may have shifted to the Ionian Sea approximately 2000 years before onset of S1 deposition, because surface waters were as cold, but saltier than surface water in the Levantine Basin during the Younger Dryas. Sapropel S1 began to form at the same time, when a significant density decrease also occurred in the Ionian Sea. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png "Palaeogeography, Palaeoclimatology, Palaeoecology" Elsevier

Temperature and salinity variations of Mediterranean Sea surface waters over the last 16,000 years from records of planktonic stable oxygen isotopes and alkenone unsaturation ratios

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Publisher
Elsevier
Copyright
Copyright © 2000 Elsevier Science B.V.
ISSN
0031-0182
eISSN
1872-616X
D.O.I.
10.1016/S0031-0182(00)00053-5
Publisher site
See Article on Publisher Site

Abstract

Alkenone unsaturation ratios and planktonic δ 18 O records from sediment cores of the Alboran, Ionian and Levantine basins in the Mediterranean Sea show pronounced variations in paleo-temperatures and -salinities of surface waters over the last 16,000 years. Average sea surface temperatures (SSTs) are low during the last glacial (averages prior to 13,000 years: 11–15°C), vary rapidly at the beginning of the Holocene, and increase to 17–18°C at all sites during S1 formation (dated between 9500 and 6600 calendar years). The modern temperature gradient (2–3°C) between the Mediterranean sub-basins is maintained during formation of sapropel S1 in the Eastern Mediterranean Sea. After S1, SSTs have remained uniform in the Alboran Sea at 18°C and have fluctuated around 20°C in the Ionian and Levantine Basin sites. The δ 18 O of planktonic foraminifer calcite decreases by 2‰ from the late glacial to S1 sediments in the Ionian Basin and by 2.8‰ in the Levantine Basin. In the Alboran Sea, the decrease is 1.7‰. Of the 2.8‰ decrease in the Levantine Basin, the effect of global ice volume accounts for a maximum of 1.05‰ and the temperature increase explains only a maximum of 1.3‰. The remainder is attributed to salinity changes. We use the temperature and salinity estimates to calculate seawater density changes. They indicate that a reversal of water mass circulation is not a likely explanation for increased carbon burial during S1 time. Instead, it appears that intermediate and deep water formation may have shifted to the Ionian Sea approximately 2000 years before onset of S1 deposition, because surface waters were as cold, but saltier than surface water in the Levantine Basin during the Younger Dryas. Sapropel S1 began to form at the same time, when a significant density decrease also occurred in the Ionian Sea.

Journal

"Palaeogeography, Palaeoclimatology, Palaeoecology"Elsevier

Published: May 15, 2000

References

  • An ocean general circulation model view of the glacial Mediterranean thermohaline circulation
    Bigg, G.R
  • Postglacial connection of the Black Sea to the Mediterranean and its relation to the timing of sapropel formation
    Lane-Serff, G.F; Rohling, E.J; Bryden, H.F; Charnock, H
  • The oxygen and carbon isotope distribution in the Mediterranean water masses
    Pierre, C
  • Late Quaternary changes in Mediterranean intermediate water density and formation rate
    Rohling, E.J; Gieskes, W.W.C
  • Mediterranean nutrient balance and episodes of anoxia
    Sarmiento, J.L; Herbert, T; Toggweiler, J.R
  • Evidence for the evolution of an oxygen minimum layer at the beginning of S-1 sapropel deposition in the eastern Mediterranean
    Ströhle, K; Krom, M
  • Redistribution and geochemical behaviour of redox-sensitive elements around S1, the most recent eastern Mediterranean sapropel
    Thomson, J
  • High fertility in the Alboran Sea since the last glacial maximum
    Vergnaud-Grazzini, C; Pierre, C
  • Benthic isotope evidence for changes of the Mediterranean outflow during the late Quaternary
    Zahn, R; Sarnthein, M; Erlenkeuser, H

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